Sympathetic transduction of blood pressure during graded lower body negative pressure
Bibliographic record
Abstract
Introduction Cross‐sectional work has demonstrated that participants with high resting muscle sympathetic nerve activity (MSNA) have lower resting sympathetic transduction of blood pressure (BP), and a larger proportion of sympathetic bursts firing above the BP set‐point (or mean BP). However, to date, most of these observations have been evaluated between participants with different levels of resting MSNA. The objective of the current study is to evaluate the influence of acute elevations in MSNA on sympathetic transduction of BP in young healthy adults using graded lower body negative pressure (LBNP). We hypothesize that sympathetic transduction will decrease during acute elevations in MSNA due to an increased proportion of MSNA bursts firing above the BP set‐point. Methods Ten (1 female) young healthy participants underwent 8 minutes of quiet rest, followed by a graded LBNP protocol consisting of 8‐minute stages at ‐10, ‐20, and ‐30mmHg. Beat‐to‐beat heart rate and BP were quantified using single‐lead electrocardiography and finger photoplethysmography, respectively, while MSNA was quantified using fibular nerve microneurography. Sympathetic transduction was quantified in the time (signal‐averaging) and frequency (MSNA‐diastolic BP low frequency [LF: 0.04‐0.15 Hz] transfer function magnitude) domains. Tertiles of diastolic BP were determined for each participant, and the proportion of MSNA bursts firings within each BP tertile were quantified. Results MSNA burst frequency increased progressively during graded LBNP (from 15±7 to 17±7, 22±7, and 27±9 bursts/min; P <0.01), while the proportion of MSNA bursts firing in the highest BP tertile remained stable (19±7, 18±9, 19±9, 19±7 %; P =0.72). Sympathetic transduction of BP was unchanged during LBNP (from 2.1±1.1 to 2.3±1.5, 2.1±1.2, and 2.0±1.1 mmHg; P =0.51), while the BP responses to non‐burst cardiac cycles decreased progressively (from ‐0.7±0.5 to ‐0.9±0.5, ‐1.0±0.4, and ‐1.4±0.7 mmHg; P <0.01). The difference between burst and non‐burst cardiac cycles (from 2.8±1.4 to 3.2±1.9, 3.1±1.5, and 3.4±1.3 mmHg; P =0.26) and the MSNA‐diastolic BP transfer function magnitude (from 0.14±0.09 to 0.14±0.06, 0.14±0.06, and 0.13±0.07 au/mmHg; P =0.40) were also unchanged during LBNP. Lastly, the change in the proportion of MSNA bursts firing in the largest BP tertile was associated with the change in signal‐averaged sympathetic transduction across each stage of LBNP (r= ‐0.79, ‐0.78, ‐0.81; P ≤0.01). Conclusion Sympathetic transduction of diastolic BP is unchanged during graded LBNP due to the heterogenous inter‐individual responses in the gating of bursts to diastolic BP. The proportion of bursts firing at high BPs are associated with changes in sympathetic transduction of BP. The determinants of gating MSNA burst occurrence by the arterial baroreflex and its capacity for modulation warrant further study.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".